System



Aug. 25. 1925.

Y Y R. TROGER PROTECTIVE SYSTEM Filed Nov. 4. 1924 i213). l.

lnven'tol Richard Tr-ci er, y His Attorney Patented Aug. 25, 1,925.

'R-IcHARD tmtienit,

COMPANY, A CORPORATION OF NEW Yong.

'Aijgmtmi filed 'iwifembe'r 4, 15924, seem. #415913;

TO dZZ/LDZLOWL it mtzy'ooncem: I 3, t

Be it known that 'I, RICHARD; Tnoeie, 'a citizen of Germany, residing at Zehlendorf, Germany, have invented certain ne end useful Improvements in Protective syetem's, of Whichthe following is a specification.

I My invention jrelates toprotective systems, and 'hilSfOlYitS object the provision of an improved errangelnefit for precluding the flow of excessive current between iiiterconnect ed electric inachinesfor soiirces which are subject to difierent electric-a1 conditions.

In many cases the interconnection of electrical machines or sources subject to "difierent electrical conditions is apt to prodhce excessive and injurious.currents. It is "Well knowh that in the paralleling of alternating current generators for exzhnple, such currents are 1ike1yt0he proclilced unless the diifiereiit generators areinphase and. are 0p crating at stibstantielly the same frequency and voltage. Likewise, the connection of an electric motor toe .soiirce of current is immediately followed by a rush of current due to the low value of the motor coiniterelect'i'oinotive force at stert-ing. In these and other cases Where excessive currents are apt to be produced, itjhas been customary to provide protective ep'pe'ratus .de'signei'to isolate the endz mngered apparatu This procedhre. is no t'always' satisfactory for the reason that "it is frequently desirable to 'rethin the c'onnectionhetiveen the differentapparetus nntil a stable operetihg' condition has been attained In accordance 'With inveiitio n the different apparatus are in; itially or perinzil iently interconnected through ti Series resonant circuit which is selectively adjustable to both frequency and current through'ahtomatic vdrialtioh of one cohiponiit of the reactenc'e in eccorda'nce With the magnitude ofthe ciir rent, a by the use of a reactor having an iron core fore)? 'aniple. e W

My invention v'vill be better understood from the fcllowihg clescription when considered infconnectioil with the accompanying drawing and its scope will he pointed out in the appended claims.

Referringto the am lugs; ig rsiibws i Fig, l shov'v s an alternatingjcnrrent iriziin 1511's 1&0 whifdh'ciirreht m y' upp from connect svvit ch 4, or from a generator 7 through OTILSWltCh 8 and disconnect switch 9. Biscohnect switches 5 and 10 areprov'ideci for connecting the generators 25nd 7 respectively, to the auxiliary bus 6. The inein bus 1 may be iiiterconnected vvith a Power transmission or distribution system which issupplied vvith'ciirrentfroni a plu- (peek: of paralleling "the variousgenera'tors erra hged to he IlltGICOfiilECtt-Zd wlth the inain hnsl, a tuned circuit is provided. This ciredit isfariahlgedtobe connected between the buses 6 by meens ofswitches 11, 12, 13"21 1 1d 14, endcomprises a condenser 15 and e reactor l fiprovided with enli'ron core 17. Where it is-desired to eeiclilde thetuned cirqitffroimhe gen-enter circuit afterthe gen e'rzit o'r been synchronized, a switch '18 connected betweeh the terminals of the bitcui tinzfly be provided. I

fItfis'vveH known the t the inductiince 61: a jrea 'ctor hztviiig in iron core changes dueto the fectfthatthe permeability 0f,the 'core varies with "the degree of its salturation. .Thiisg when the core "is operating at a low degree be semmit on, he :inauctenee o the reactor is co rhpai eti'velyjhig h and when the core is saturated, the "inductance 'o' i the reii ifi ior pi fi il l -i PJ d -P t 'ot'saithreti'on, refore,- the in'diic'tance "of the reactor is determined y-[the magnitude of fee im e which it "ca'rr'ie If such s'lttth't frequency, theiiieximiiin value f curn. the re t .resonance is said to exist.

conditions, the circuit operates as if it contained only resistance and a condition of Upon closure of the circuit comprising condenser 15 and reactor 16 therefor, there will be a tendency for the current supplied through this c1rcuit to increase in value, thereby reducing the reactance of the reactor 16 until it is substantially equal to that of the condenser 15. When this occurs, any further changes in the current value will increase or decrease the reactance of the reactor 16, thus changing the tuning of the circuit and immediately bringing into operation a force tending to maintain the current at a value predetermined by the frequency at wh ch current is supplied and the characteristics of the condenser and reactor.

Assuming the switches to be in their illustrated positions, the circuit comprising condenser 15 and reactor 16 to be tuned for the frequency at which the bus 1 is operating and the generator 7 to be excited, the current supplied to the generator 7 will immediately increase to a value predetermined by the characteristics of the circuit comprising condenser 15 and reactor 16. lVhen the speed of the generator 7 is increased, it will tend to supply current of variable frequency to the bus 1, but so long as its frequency is substantially dilferent from that of the generator 2 and the main bus 1, this current will be limited to a low value by the impedance of the tuned circuit. As the frequency of the generator 7 more nearly approaches that of the bus, the synchronizing force exerted between the generator and the bus increases until the generator assumes the same phase and frequency as that of the bus. Under these conditions, the value of the current transmitted between the generator and bus is free to assume a value predetermined by the characteristics of the tuned circuit and a condition of complete synchronism may be established by varying the excitation of the generator 7 until its voltage becomes equal to that of the bus. When a condition of synchronism has been established, the switch 18 may be closed to shortcircuit the tuned circuit, the switch 9 may be closed to connect the generator 7 directly to the bus 1, and the switch 10 may be opened to release the auxiliary bus and tuned circuit for use in paralleling other generators with the system.

As will be readily understood, my invention is not limited to the paralleling of generators but is capable of many different uses. In the case of a small power station controlled from a distance, a generator may be accelerated and synchronized by connecting it to the line through the tuned circuit and starting its prime mover. If the tuned circuit is designed for the full load current of the generator, it may be permanently retained in the circuit, thus serving to limit the load supplied from station and to limit the current transmitted between the system and station under all conditions of operation.

Fig. 2 shows a motor 19 arranged to be supplied with current from the bus 1 through a switch 20 and a tuned circuit comprising condenser 15 and reactor 16. A switch 21 is provided for short-circuiting the tuned circuit when it is desired to utilize it only during starting. In View of what has been said, it will be readily understood that the starting current of the motor 19 is predetermined by the characteristics of the tuned circuit. If desired, the tuned circuit may be designed for the full load current of the motor and utilized during operation of the motor as a protective device.

Fig. 3 shows a pair of machines 22 and 23 mounted on a common shaft 24 and arranged to interchange power between two electric systems 25 and 26 in a manner well understood by those skilled in the art. It is well known that variations in the frequencies of the systems 25 and 26 are apt to overload the machines by which these systems are interconnected. In order to protect the machines 22 and 23 against overload, tuned circuits similar to that previously described are interposed between them and the lines to which they are connected. While I have shown each machine as protected by a tuned circuit, it will be apparent that one tuned circuit will in most cases afford adequate protection for both machines.

As will be apparent to those skilled in the art. my invention is capable of a variety of applications and permits of many modifications. I therefore aim in the appended claims to cover all arrangements and modifications which fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is,-

1. A protective system for precluding the interchange of excessive current between alternating current circuits required to be interconnected'when subject to different electrical conditions, comprising a circuit arranged to be tuned at apredetermined frequency and a predetermined current, and means for connecting said circuit between said alternating current circuits.

2. A protective system for precluding the interchange of excessive current between alternating current machines required to be interconnected when subject to different electrical conditions, comprising a circuit arranged to have its tuningvaried in accordance with the transmission of current therethrough and to be resonant at a predetermined frequency with a predetermined current, and means for connecting said circuit between said machines.

rated at a predetermined current, and means for connecting said circuit between said machines.

In witness whereof, I have hereunto set my hand this 17th day of October, 1924.

RICHARD TRCGER. 

